A Computationally Efficient Modeling Code for Sh-Waves in Austenitic Welds Using an Explicit Space-Time Green-Function

For ultrasonic inspection of austenitic welds and cladded components horizontally polarized shear (SH) waves — as generated by electromagnetic acoustic transducers (EMATs) — have certain benefits compared with quasi-vertically polarized shear and quasi-pressure waves. SH-waves suffer the least distortion of all three wave modes when propagated through anisotropic weld material and no energy is lost through mode conversion at the steel/free surface or base metal/weld interfaces. To explain experimentally observed phenomena and to predict the cases where SH-waves might be best employed, modeling of the respective wave propagation effects is useful. In this contribution, a computationally efficient modeling code is presented for SH-waves propagating in transversely isotropic media, thus particularly applicable to ideally fiber-textured austenitic weld material. An explicit space-time domain far-field representation of Green’s dyadic function has been derived with respect to the wave type under concern, the fiber direction being included as a free parameter. The obtained relationships have been applied to the Generalized Point-Source-Synthesis method (GPSS [1,2]) to model radiation, propagation and scattering effects. The code thus improved — SH-GPSS— is characterized by a considerable reduction of computer run-time and is therefore particularly convenient in view of a respective extension to inhomogeneous weldments. Numerical results are presented for both continuous wave and time-dependent rf-impulse modeling for austenitic weld metal specimens, covering field profiles as well as wave front snapshots for a phased array EMAT-probe

A Mumps Outbreak in Vojvodina, Serbia, in 2012 Underlines the Need for Additional Vaccination Opportunities for Young Adults

In 2012, mumps was introduced from Bosnia and Herzegovina to Vojvodina, causing an outbreak with 335 reported cases. The present manuscript analyses the epidemiological and laboratory characteristics of this outbreak, identifies its main causes and suggests potential future preventive measures. Sera of 133 patients were tested for mumps-specific antibodies by ELISA and 15 nose/throat swabs were investigated for mumps virus RNA by RT-PCR. IgG antibodies were found in 127 patients (95.5%). Mumps infection was laboratory-confirmed in 53 patients, including 44 IgM and 9 PCR positive cases. All other 282 cases were classified as epidemiologically-confirmed. More than half of the patients (n = 181, 54%) were 20-29 years old, followed by the 15-19 age bracket (n = 95, 28.4%). Twice as many males as females were affected (67% versus 33%). Disease complications were reported in 13 cases (3.9%), including 9 patients with orchitis and 4 with pancreatitis. According to medical records or anamnestic data, 190 patients (56.7%) were immunized with two doses and 35 (10.4%) with one dose of mumps-containing vaccine. The Serbian sequences corresponded to a minor genotype G variant detected during the 2011/2012 mumps outbreak in Bosnia and Herzegovina. Vaccine failures, the initial one-dose immunization policy and a vaccine shortage between 1999 and 2002 contributed to the outbreak. Additional vaccination opportunities should be offered to young adults during transition periods in their life trajectories

Entwicklung eines koppelmittelfreien Ultraschall-Prüfsystems zur wiederkehrenden Prüfung des innenoberflächennahen Bereichs der Tankschweißnähte 1 und 6 des SNR 300

Für die Ergänzung der zur Zeit vorgegebenen wiederkehrenden Prüfungen am Reaktortank des KKW-Kalkar - im wesentlichen optische Inspektion mit Fernsehkameras - wird ein zerstörungsfreies Prüfverfahren auf Ultraschallbasis entwickelt und qualifiziert, das eine zerstörungsfreie Prüfung des innenoberflächennahen Bereichs der Tankwand im Bereich der Rundachweißnähte 1 (ferritische Naht) und 6 (ungepufferte Mischnaht zwischen dem ferritischen und austenitischen Teil des Behälters) ermöglichen soll. Diese Entwicklung wird vom BMFT gefördert und in enger Zusammenarbeit und Abstimmung mit der Firma Interatom und einem Manipulato-Hersteller durchgeführt. Die vorliegende Prüfaufgabe verlangt den Einsatz von Ultraschallwellen, die die Oberfläche und den oberflächennahen Bereich erfassen. Dazu gehören neben den Rayleighwellen die streifend eingeschallten, tangential polarisierten Transversalwellen (SH-Wellen). Diese werden an der Trennfläche Grundmaterial/Schweißgut einer austenitischen oder Misch- Schweißnaht durch Impedanzanpassung zu 100% in das Schweißgut übertragen werden, was von wesentlicher Bedeutung für die Prüfbarkeit ist. Das Senden und Empfangen dieser Wellen muß auf koppelmittelfreie Art und Weise erfolgen, da an der Innenoberfläche mit Natriumresten zu rechnen ist. Mit Hilfe der elektromagnetischen Ultraschall(EMUS)-Technologie werden die für die Oberflächenprüfung der Schweißnähte besonders gut geeigneten SH-Wellen effektiv und koppelmittelfrei angeregt und empfangen. Die Umbegungsbedingungen - Temperatur und Strahlenbelastung - sind bei EMUS-Prüfköpfen durch Einsatz entsprechender temperatur- und strahlungsbeständiger Materialien beherrschbar. Es wird über Ergebnisse zur Längs- und Querfehlerprüfung berichtet

Monitoring the filling level of the RPV using stationary EMUS-probes

Today the filling level in the reactor pressure vessels (RPV) of a boiling water reactor is measured exclusively by the approved differential pressure method based on a comparison of columns of weights. Because of the high importance which the filling level in the RPV respresents for the safety of a nuclear power plant, a physically diverse measuring method has been searched for which satisfies the following requirements: -unequivocal signal generation, - sufficient precision, -good time behavior, -possibilty of installation in existing plants. A binary working ultrasonic method, with which discrete marks of the filling level in the RPV can be surveyed, fulfils these requirements. (-z-

Weiter-Entwicklungen und praktische Anwendungen der EMUS-Technik

Die elektromagnetische Ultraschall (EMUS)-Wandlung hat sich in den letzten Jahren als eine für viele praktische Anwendungen geeignete Technik erwiesen. Unterschiedliche Prüf- und Meßverfahren wurden damit realisiert. Zwischenzeitliche Weiter-Entwicklungen des Hochfrequenzteils der Prüfköpfe haben dazu geführt, daß die notwendigen Vormagnetisierungs-Induktionsdichten um den Faktor 2-3 niedriger sind als bei EMUS-Prüfköpfen mit "konventionellem" HF-Teil bei vergleichbarer Schall-Intensität. Da diese Indiktondichten bereits mit kleinvolumigen Permanent-Magneten erreicht werden, konnten sehr kompakte, verschleißarme Prüfkopf-Ausführungen realisiert werden. Dies eröffnet eine Reihe von neuen Anwendungen. Es werden der grundsätzliche Aufbau dieser Prüfköpfe beschrieben und deren Vor- und Nachtiele gegenüber konventionellen EMUS-Wandlern aufgezeigt. Die spezifische Eigenschaften und die sich daraus ergebenden praktischen Anwendungen werden vorgestellt: -Warmfester Aufbau zum Einsatz bei erhöh ten Temperaturen bis ca. 300 Grad Celsius ohne Kühlung zur Kontrolle des Füllstandes in Behältern und Rohrleitungen. -Sehr geringes Prüfkopfvolumen und verschleißarme Ausführung zum Einsatz an komplizierten Geometrien (Schienen) und zur Innenprüfung von Rohrleitungen. -Mehrprüfkopf-Anordnungen zur flächendeckenden Prüfung von Oberflächen (Grobblechen). -Erweiterter Frequenzbereich für Oberflächenwellen zur Charakterisierung von oberflächennahen Kriechschäden über US-Geschwindigkeitsmessung

Numerical Time Domain Modeling of the Ultrasonic NDT with Electromagnetic Acoustic and Piezoelectric Transducers

In this paper, the 2-D numerical simulation or two typical ultrasonic NDT situations applying two types of ultrasonic transducers - piezoelectric transducers and EMAT - has been considered. In the numerical modeling the coupling between electromagnetic and elastodynamic filed quantities has been neglected. An approximated elastodynamic model for the coupling between the transducer and the solid in excitation and reception mode has been applied and implemented in the solid in excitation and reception mode has been applied and implemented in the well-established numerical modeling code EFIT. The 2-D numerical results showed for the selected parameters, that the used elastodynamic model leads to realistic results, which have been validated against measurements. In future work, one could include the electromagnetic-elastodynamic coupling between the EMAT and solid material as well as the driving electrical network, which has been already presented for a piezoeletric transducer

Dry UT by guided shear horizontal using EMAT's

Ultrasonic Testing (UT) is still concentrated on the 'classical' wave modes generated by piezoelectric probes. Other wave modes as the Shear Horizontal (SH) waves and the wide class of guided waves offer new solutions for UT not yet widely used due to the lack of availability of appropriate probes and equipments. EMAT's are the most far developed ultrasonic probes for UT using SH-waves and guided waves. Despite their limitations (efficiency, lift off-effect, frequency range etc.) they have the big advantage to perform dry UT. This contribution will present new solutions for UT of metallic parts using guided Shear Horizontal waves: for the in-line inspection for defects and weld geometry of butt welds, for crack inspection in gas pipelines, for screening UT for hidden corrosion in tubular goods, for long range inspection of pipes and for the inspection of multilayered aircraft components. The latest developments of the probe design are shortly reported. The equipments and their integration in production lines as well for in-service application are shown together with examples of inspection results during their practical applications